builtin rebase: use no-op editor when interactive is "implied"

Some options are only handled by the git-rebase--interactive backend,
even if run non-interactively. For this awkward situation (run
non-interactively, but use the interactive backend), the shell scripted
version of `git rebase` introduced the concept of an "implied
interactive rebase". All it does is to replace the editor by a dummy one
(`:` is the Unix command that takes arbitrary command-line parameters,
ignores them and simply exits with success).

Signed-off-by: Pratik Karki <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: prertik

builtin/rebase.c

@@ -383,6 +383,13 @@ static int run_specific_rebase(struct rebase_options *opts)
 	add_var(&script_snippet, "git_format_patch_opt",
 		opts->git_format_patch_opt.buf);
 
+	if (is_interactive(opts) &&
+	    !(opts->flags & REBASE_INTERACTIVE_EXPLICIT)) {
+		strbuf_addstr(&script_snippet,
+			      "GIT_EDITOR=:; export GIT_EDITOR; ");
+		opts->autosquash = 0;
+	}
+
 	switch (opts->type) {
 	case REBASE_AM:
 		backend = "git-rebase--am";